diff --git a/types/index.d.ts b/types/index.d.ts
index 41d383d5..92ea2263 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -79,7 +79,7 @@ export class Asset {
   toXDRObject(): xdr.Asset;
   toChangeTrustXDRObject(): xdr.ChangeTrustAsset;
   toTrustLineXDRObject(): xdr.TrustLineAsset;
-  contractId(): string;
+  contractId(networkPassphrase: string): string;
 
   code: string;
   issuer: string;